The Doctor was the most trusted medically-trained human in the young Ape City established by Caesar. When Cornelius was gravely ill, she was sent for to treat the young chimp and thus escaped being detained in the corral (whether her training was in human or animal medicine isn't stated). Her professional opinion was respected by Caesar and Lisa and her advice followed. In the Marvel Comics adaptation based on early draft scripts, more of her life was depicted, including her illicitly eating a cooked rabbit with other humans, in defiance of Caesar's law prohibiting meat.